A CB1 neutral antagonist blocked fentanyl effects in rats without the side effects of rimonabant
The CB1 neutral antagonist AM4113 blocked fentanyl discrimination in rats at lower doses and without the response-suppressing side effects seen with rimonabant, supporting its potential as a novel opioid use disorder treatment.
Quick Facts
What This Study Found
AM4113 (0.32-1.0 mg/kg) effectively blocked fentanyl discrimination at doses that did not reduce food-maintained responding. Rimonabant (1.0-10 mg/kg) only partially attenuated fentanyl effects at the highest dose, which also significantly decreased response rates. Mu-opioid agonists fully substituted for fentanyl, confirming opioid mediation.
Key Numbers
AM4113 effective doses: 0.32-1.0 mg/kg. Rimonabant partial effect only at 10 mg/kg (with rate suppression). AM4113 was effective at 10-fold lower doses than those affecting food responding.
How They Did This
Male rats trained to discriminate 0.032 mg/kg fentanyl from saline under a fixed-ratio 10 schedule of food reinforcement. Tested effects of CB1 neutral antagonist AM4113 and inverse agonist rimonabant on fentanyl discrimination and food-maintained responding.
Why This Research Matters
Current opioid use disorder treatments are limited. A CB1 neutral antagonist that blocks fentanyl effects without the psychiatric side effects that ended rimonabant could offer a new therapeutic approach.
The Bigger Picture
The functional interaction between cannabinoid and opioid systems opens a novel therapeutic avenue for the opioid crisis, particularly since CB1 neutral antagonists may avoid the depression and anxiety that doomed rimonabant.
What This Study Doesn't Tell Us
Animal study in rats. Drug discrimination assay measures subjective effects, not addiction-related behaviors. Only male rats tested. Translation to human opioid use disorder uncertain.
Questions This Raises
- ?Would AM4113 also block the reinforcing properties of fentanyl in self-administration models?
- ?Could CB1 neutral antagonists be used alongside existing opioid treatments?
Trust & Context
- Key Stat:
- AM4113 blocked fentanyl effects at 10x lower doses than those affecting food intake
- Evidence Grade:
- Well-designed animal pharmacology study with appropriate controls, but requires human translation.
- Study Age:
- Published in 2022.
- Original Title:
- Effects of the cannabinoid CB1-receptor neutral antagonist AM4113 and antagonist/inverse agonist rimonabant on fentanyl discrimination in male rats.
- Published In:
- Drug and alcohol dependence, 240, 109646 (2022)
- Database ID:
- RTHC-03666
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Could cannabinoid drugs help treat opioid addiction?
In rats, a CB1 neutral antagonist (AM4113) effectively blocked fentanyl's subjective effects without the side effects that ended the previous CB1 drug rimonabant, suggesting a promising new approach.
What is a neutral antagonist?
Unlike inverse agonists like rimonabant that push receptor activity below baseline (causing depression and anxiety), neutral antagonists simply block the receptor without shifting its baseline activity.
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Cite This Study
https://rethinkthc.com/research/RTHC-03666APA
AlKhelb, Dalal; Kirunda, Andre; Ho, Thanh C; Makriyannis, Alexandros; Desai, Rajeev I. (2022). Effects of the cannabinoid CB1-receptor neutral antagonist AM4113 and antagonist/inverse agonist rimonabant on fentanyl discrimination in male rats.. Drug and alcohol dependence, 240, 109646. https://doi.org/10.1016/j.drugalcdep.2022.109646
MLA
AlKhelb, Dalal, et al. "Effects of the cannabinoid CB1-receptor neutral antagonist AM4113 and antagonist/inverse agonist rimonabant on fentanyl discrimination in male rats.." Drug and alcohol dependence, 2022. https://doi.org/10.1016/j.drugalcdep.2022.109646
RethinkTHC
RethinkTHC Research Database. "Effects of the cannabinoid CB1-receptor neutral antagonist A..." RTHC-03666. Retrieved from https://rethinkthc.com/research/alkhelb-2022-effects-of-the-cannabinoid
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.